Static and kinetic friction

Answer Key - Grade 11 Science Worksheet - Building Confidence

Circle the best answer, or write your answer on the line.

1. 1.

   A 5 kg box slides across a level floor with μk = 0.3. With g = 9.8 m/s², what is the kinetic friction force, Ari?

   14.7 N
2. 2.

   A 6 kg box slides across a level floor with μk = 0.4. With g = 9.8 m/s², what is the kinetic friction force, Bo?

   23.52 N
3. 3.

   A 20 kg box slides across a level floor with μk = 0.15. With g = 9.8 m/s², what is the kinetic friction force, Esme?

   29.4 N
4. 4.

   “Free-body diagram (example data): a box pushed across the floor” In the free-body diagram, how big is the friction force, Jun?

   • 58.8 N
   • 12 N
   • 0 N, since it is moving
5. 5.

   In the free-body diagram, how big is the static friction force, Kira?

   • 0 N
   • 5 N
   • 196 N

6. Read this first

   Free-body diagram (example data)

   a block sliding to the left of mass 2 kg, with arrows from its center: weight 19.6 N down; normal force 19.6 N up; friction ? N ?.

7. 6.

   In the free-body diagram, which way does friction point on the block, Luz?

   • Straight up
   • To the right
   • To the left, with the motion
8. 7.

   Which usually takes a bigger push: getting a heavy box started, or keeping it sliding, Noah?

   • Getting it started
   • They take the same push
   • Keeping it sliding
9. 8.

   A box finally starts to slide. What happens to the friction force on it, Pia?

   • It vanishes
   • It jumps up
   • It drops a little
10. 9.

    A block slides east across a table. Which way does friction act on it, Ren?

    • East, with the motion
    • West
    • Down into the table
11. 10.

    A puck slides north across rough ice. Which way does friction act on it, Zee?

    • East
    • North
    • South